This invention relates to apparatus for forming thin films in quantity, and more particularly relates to a plasma CVD apparatus which is suitable for mass-production.
Recently, ECR (Electric Cyclotron Resonance) CVD has attracted the interest of researchers as a new method of manufacturing thin films, particularly amorphous thin films. For example, Matsuo et al discloses one type of such ECR CVD apparatus in U.S. Pat. No. 4,401,054. This recent technique utilizes microwave energy to energize a reactive gas such that it develops into a plasma. A magnetic field functions to pinch the plasma gas within the excitation space. Within this excitation space, the reactive gas can absorb the energy of microwaves. A substrate to be coated is located distant from the excitation space (resonating space) for preventing the same from being spattered. The energized gas is showered onto the substrate from the resonating space. In order to establish electron cyclotron resonance, the pressure in a resonating space is kept at 1.times.10.sup.-5 Torr at which pressure electrons can be considered as independent particles and resonate with the microwave energy in an electron cyclotron resonance on a certain surface on which the magnetic field strength meets the requirement for ECR. The excited plasma is extracted from the resonating space, by means of a divergent magnetic field, and is conducted to a deposition space which is located distant from the resonating space and in which there is disposed a substrate to be coated.
In such a prior art method, it is very difficult to perform carbon deposition of a polycrystalline or single-crystalline structure, so that currently available methods are substantially limited to processes for manufacturing amorphous films. Also, high energy chemical vapor reaction can not be readily accomplished by such a prior art and therefore it has not been possible to form diamond films or other films having high melting points, or uniform films on a surface having depressions and caves can not be formed. Furthermore, it was impossible to coat the surface of a super hard metal such as tungsten carbide with a carbon film. Because of this it is necessary to coat a super hard surface with a fine powder of diamond for use of abrasive which has a sufficient hardness and to make sturdy mechanical contact between the diamond powder and the substrate surface. Particularly, the throughput of substrates accommodated in one chamber is too low to apply for commercial base production.